An ideal system for topically delivering an active ingredient should be as stable as possible and should deliver the ingredient in a manner such that it adheres to the skin for sufficient periods to obtain the required therapeutic or other benefits while other non-therapeutic components of the delivery system evaporate or are otherwise removed from the area of treatment. In an effort to develop an effective delivery system, Dow Corning has developed volatile silicone fluids, such as polydimethylcyclosiloxane, cyclomethicone and hexamethyldisiloxane, for use in formulating water-in-oil emulsions. Such emulsions are taught by Dow Corning to be useful as cosmetics solvents, to improve lubricity and spreading properties of skin creams, lotions, bath oils, and suntan, shaving and stick products and in hair grooming products such as hair sprays and conditioners. One Dow Corning product, namely, Q2-3225C, which is a dispersion of cyclomethicone and dimethicone copolyol, is said to be useful in preparing water-in-oil emulsions which are delivery systems for cosmetic ingredients such as emollients, moisturizers, sunscreens, antiperspirant salts and pigments. Furthermore, Dow Corning indicates that such emulsions feel very rich as they are applied, but quickly dry down to leave only the nonvolatile ingredients on the skin.
The stability of the Dow Corning water-in-oil emulsions containing cyclomethicone is increased by including an electrolyte in the aqueous phase, such as sodium chloride, sodium citrate, magnesium sulfate or aluminum chlorohydrate in a concentration of 1 to 3% by weight.
In preparing the Dow Corning water-in-oil emulsion, silicon block polymers, such as dimethicone copolyol, are employed as the primary emulsifier whereas Pareth-15, which is a polyethylene glycol ether of a mixture of synthetic C.sub.11-15 fatty alcohols with an average of 3 moles of ethylene oxide, is employed as a silicone co-emulsifier.
The Dow Corning system is an excellent means for delivering only certain types of active ingredients which are compatible with the volatile silicone and the emulsifiers employed. Thus, such system may be limited in its range of acceptability of active ingredients with which it may be employed.